PDGFRA and neoplasm: As shown in Figure 2, in 14 out of 15 GISTs with a KIT mutation and in 2 out of 10 GISTs with a PDGFRA mutation, the relative expression of KIT was 1.47 arbitrary units (a.u.)or greater, while in the remaining tumours, it was 0.37 a.u. or lower.